This section provides background information related to the present disclosure which is not necessarily prior art.
Shotshells can propel a single projectile, such as a slug, or more commonly, multiple projectiles, such as birdshot or buckshot. The dispersion of multiple shot pellets at a given distance from the muzzle affords a greater chance of hitting a moving target than the singular path of a slug. Thus, a moderate dispersion rate is desirable for some applications, such as waterfowl, upland, and rabbit hunting where the intended target is moving. However, in some applications, such as turkey hunting, the intended target is relatively motionless and small. In these types of applications, it can be desirable to have a tighter pattern, with less shot dispersion.
The rate of dispersion of multiple projectile loads can be influenced by gun systems and cartridge design. Tighter constrictions or “choke” in the muzzle section of the barrel can reduce the dispersion rate of shot pellets to some degree. Cartridge design elements, such as shot type, wad type, and buffering can also reduce dispersion rate.
Lead was the material of choice for early cartridges because of its density, relatively low cost, and easy formability. The easy formability however was also a negative. Soft lead pellets are deformed when subjected to the high acceleration forces of cartridge ignition and with direct barrel contact while being accelerated toward the muzzle. Early cartridges did not incorporate any shot wad systems. Soft lead shot had direct contact with the barrel. This resulted in a considerable dispersion rate. Eventually wads and shot cups provided a liner or barrier between the shot and barrel to reduce pellet deformation associated with bore contact. U.S. Pat. No. 3,092,026, incorporated granulated particles intermixed in the shot column to “buffer” the pellets during acceleration to reduce deformation further. These feature elements reduced dispersion rate. Alternate shot materials, such as steel or tungsten, maintain spherical shape to reduce dispersion, but have other shortcoming, such as low density or extremely high cost.